The proposal consists of two parts. In the first our aims are to continue the current studies on genetically predetermined structural polymorphism of M-N glycoprotein (glycophorins A) among human individuals. We plan to focus on details of amino acid sequences and carbohydrate structures of two regions of the molecule isolated from erythrocyte membranes of single donors, the amino terminal octapeptide which includes three 0-glycosidically bound carbohydrate units and a region which adjoins and includes the N-asn linked unit. We will examine glycoproteins of additional individuals who are immunologic variants of the MN blood group types. Our evidence suggests that variants of the carbohydrate structures may exist; we plan to examine glycoproteins of additional randomly chosen individuals to further document this finding. To ascertain whether variants of the oligosaccharide units are genetically predetermined we will examine, glycoproteins of members of the families of the donor. In the second part of the proposal we will study the biogenesis of this glycoprotein in human leukemic cell line K562 and human bone marrow cells as a function of erythroid differentiation. In the K562 we will more precisely document and extend the studies of others on the nature of the oligosaccharide units in M-N glycoproteins. We plan to set up long term human bone marrow cultures for use in studies of the development of the M-N glysoproteins as a function of erythroid differentiation. We propose to adapt the current approaches of Eaves et al. with long term cultures of mouse bone marrow cells to cultures of human cells and plan to obtain BFU-E at different stages of maturation. In these cells we plan to establish the presence of intermediate and fully flycosylated molecules, correlated their appearance on the membrane with the synthesis of hemoglobin and plan to examine the temporal events in the biosynthesis and assembly of the two sypes of carbohydrate units and their structural features. We hope to establish whether the glycoprotein becomes modified as a function of differentiation.